Varying interfacial reaction patterns in (VNbTaMoW)C ceramic joints brazed with Ti-Zr-Ni-Cu filler alloy

Abstract

The brazing of (VNbTaMoW)C ceramic with TiZrNiCu active filler is systematically studied. The metallurgical connection relies on two temperature-dependent patterns of interfacial reactions. At a low brazing temperature of 900°C, active Zr dominates interfacial reactions by seizing C atoms in HETMC lattice, generating a continuous (Zr, Ti, Nb)C layer and leading to the transformation of HETMC into a non-stoichiometric HETMC'. The continuous reaction layer is the weak area of joints, resulting in a shear strength of only 83MPa. The interfacial reaction pattern becomes dominated by active Ti as the brazing temperature is increased. The continuous (Zr, Ti, Nb)C layer is transformed into a flocculent (Zr, Ti, Nb)C' and partial HETMC' is decomposed into high-entropy intermetallic and (Ti, Nb, Ta, Zr)C particles. The improved interfacial structure enhanced the load-bearing capacity of joints, enabling the joint obtained at 980°C for 10min to deliver the highest shear strength of 193MPa.